require PHP 5.6+

composer.json

@@ -18,7 +18,7 @@
         "psalm": "@php ./vendor/bin/psalm --no-cache --show-info=false "
     },
     "require": {
-        "php": ">=5.2"
+        "php": ">=5.6"
     },
     "require-dev": {
         "ext-mysqli":  "*",
@@ -28,7 +28,7 @@
         "php":  ">7.2.0",
         "php-coveralls/php-coveralls" : "*",
         "phpunit/phpunit": "^6.0",
-        "vimeo/psalm":"3.0.8",
+        "vimeo/psalm":"^3.0",
         "zendframework/zendframework1": "^1.12.0"
     },
     "autoload": {